1. Field of the Invention
The present invention relates to an automatic protection switching (APS) system for an asynchronous transfer mode (ATM) exchange network.
2. Description of the Related Art
Recent advances in exchange network technology have led to use of ATM exchange networks in addition to integrated service digital networks (ISDNs). In an ATM exchange network, all communication information from tens of bits per second to hundreds of megabits per second are divided into fixed length packets or cells each composed of several tens to 128 octets, are transferred onto a transmission line of at least a 150 Mbps speed in a mixed fashion, and are subjected to high speed processing by high speed packet exchange.
From the viewpoint of the supervision and control of a digital network, in the past a large amount of overhead, such as for the transfer of line error detection information and line quality information, and the data communication, etc. was provided. Part of the overhead, for the purpose of preventing the suspension of service due to occurrence of a line failure, was provided with the APS function for automatically switching to a standby line upon the occurrence of a failure. Such an APS function, however, has never been provided in an ATM exchange network.